Yamaha digital piano P-60 keys don't work randomly (playing demo is fine)

Thread Starter

moniica

Joined Jun 10, 2020
3
I bought a used Yamaha digital piano P-60. It has the following severe issues:
  1. All keys and the control buttons don't work randomly. "Not working" means when I press down a key, no sound comes out from the speakers.
  2. It's not about any specific key. It happens to random key. Sometimes all keys have no sound.
  3. Sometimes the Demo button and Voice button don't work either.
  4. Sometimes the voice changes automatically (e.g. from piano sound to organ sound). It's like the Voice button is pressed by a ghost.
Basically this digital piano is unplayable. But it has the following good:
  1. It can play demo for hours without any problem. Looks like the main chip is good.
  2. Volume control (slider) works well.
  3. No key has exceptionally high or low sound.
I am a software engineer and has some arduino experience. I have very little knowledge about circuit board. I had several hypotheses:
  1. Hypothesis 1: the power adapter is faulty. I tried another power adapter. No change.
  2. Hypothesis 2: there is loose connector. I opened the piano several times but didn't see any loose connector. I unplugged some connectors and plugged them again. No difference.
  3. Hypothesis 3: some capacitors are faulty. I didn't see any bulging capacitors. I used an auto-range multi meter to measure some capacitors, but the values did not make sense. Later I knew it's hard to measure on-board capacitor's capacity with the normal multi meter. I searched the internet and watched some videos. I still believe they may be something wrong with the capacitors.
Hope some experts can help me. I will upload some pictures of the PCB. Thanks in advance.
 

Thread Starter

moniica

Joined Jun 10, 2020
3
Motherboard (?)IMG_7914.jpgIMG_7917.jpg






A long PCB

IMG_7905.jpg

IMG_7907.jpg

IMG_7908.jpg





Output?

IMG_7810.jpg





A small PCB for volume control, demo button, voice button.

IMG_7899.jpg





Some other images

IMG_7909.jpg

IMG_7912.jpg
 
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